The present invention relates to a touch switch with a keypad.
Touch switches of this kind are described in EP 0 054 306 A1, DE 42 07 772 C2 and U.S. Pat. No. 5,594,222. Such touch switches perform the switching action not because the operator moves a switch part but because the hand or finger of the operator changes the capacity, the lines of force or the optical reflection of the touch switch.
Also known are translucent touch switches for the input of data to video screens, which are based on optical, capacitive or resistive principles.
In DE 197 12 137 A1 a touch switch is described in which the piezo effect is utilized.
Since in touch switches of this kind no keys are mechanically moved, the operator lacks tactual feedback of the switching operation. In order nevertheless to give the operator feedback, acoustical or optical signals are alternatively generated as feedback. Many operators, however prefer direct tactual feedback to an acoustical or optical signal. It is also known that a person reacts more slowly to optical and acoustical stimuli than to tactile stimuli.
The invention is addressed to the problem of proposing a touch switch of the kind referred to above, which will give a tactual feedback when operated.
The above problem is solved by the invention in that a transducer is provided which, when the keypad is touched, impresses a movement thereon.
This brings it about that, when the operator touches the keypad the transducer impresses a movement thereon virtually simultaneously. The operator thus receives a tactical feedback of the operating action. The movement may be a brief pulse or a vibration.
It is an advantage of tactual feedback that it is felt only by the operator, and in contrast to acoustical or optical feedback it cannot be perceived by bystanders. Thus the privacy of operation is improved, which is considerable in the case of bank teller machines.
Such tactual feedback can be used in any apparatus which is operated by touch switches, such as glass ceramic cooktops in which the touch switches are integrated into the glass ceramic cooktop, keypads for stoves, cook ovens and microwave ovens, touch screens in computers, such as PC""s, laptops, and personal digital assistants. They can also be used in input terminals on bank teller machines, slot machines, remote controls, mobile telephones, controls for computer games, photographic apparatus and office machines.
In the embodiment of the invention, in the case of a keypad with a plurality of touch zones, each touch zone has its own transducer. Tests have shown, however, that it is sufficient in the case of a keypad with a plurality of touch zones to provide only a single transducer. This single transducer suffices to make the feedback perceptible in all touch zones. The distance from the transducer to the individual touch zones increases as the modulus of elasticity of the material of the keypad increases. The local relationship between the transducer and a particular touch zone is less important functionally than the time lapse between the touching of the switch surface or its particular touch zone and the tactile signal. The tactile signal is to occur in the period in which the operator usually holds his finger on the touch zone. Thus there is a possibility for arranging the transducer outside of the range in which touch zones and display devices, if any, are provided.
Preferably the keypad is a continuous glass, glass ceramic or plastic surface. The keypad can be an area of larger surface which serves other purposes, such as a display function and/or cooking function.
Preferably the transducer is a piezoceramic element or an electromagnetic transducer.
The transducer can be connected to the keypad such that it transfers its movement to the keypad. However, it can also be placed close by the keypad such that it knocks against the keypad. This can be provided especially in a magnetically operated transducer. Thus a certain interval exists between the moving part of the electromagnetic transducer and the keypad.
In an embodiment of the invention the transducer is the same piezoceramic element that is also the sensor detecting the touching of the keypad or touch zone, in which case the piezoceramic element acts first as a sensor upon contact and then as a transducer. Thus the same piezoceramic element simultaneously triggers the switching function of the touch switch and the feedback.
In another embodiment the frequency and/or the intensity (amplitude) of the movement of the transducer when different touch zones of the keypad are touched is made tactually different. The user can thus know without looking, in case of the successive touching of touch zones, whether the desired input made by the previous touch zone contact has been made correctly. The transducer thus gives the operator not only feedback of the touching of the touch zones but also confirmation of the reading of the entry.
In a further embodiment of the invention, the duration and/or frequency and/or intensity (amplitude) of the movement of the transducer is dependent upon the duration of the contact with the keypad or touch zone. This is advantageous whenever different values are set according to the duration of contact. For example, in many touch switches the input value is increased or reduced by longer contact. By this embodiment the tactual feedback is matched to the entry. For example, it can be used in a photographic apparatus to provide tactile perception of the operation xe2x80x9cset autofocusxe2x80x9d and xe2x80x9cshoot.xe2x80x9d
Various other objects, advantages, and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.